Piston



R. D. CROW.

PISTON.

APPLICATION FILED MAR. 22, I921.

Patented Apr. 4, 1922.

Fig.1

ROBERT DOUGLAE CROW, INVENTOR.

H is ATTORNEY.

ROBERT D. CROW. OF HOUSTON, TEXAS.

PISTON.

To all whom it may concern Be it known that I, ROBERT D. CROW, a citizen of the United States, residing at Houston, Harris County, Texas, have invented a certain new and useful Improvement "in Pistons, of whichthe following is a full, clear. and exact description, such as will enable others skilled in the art to which it appertains to make and use the same.

' My invention relates to pistons and has particular application to pistons for use in internal combustion motors.

In such motors the piston must be adapted to operate under high speed and be subjected to high temperature. Because of its' a result the aluminum piston must be made appreciably smaller than the interior dimensions of the cylinder to allow for the said greater expansion of the piston. "This leads to poor compression and to leakage of gas \and oil past the piston. Furthermore, alum inum wears excessively when highlyheated and the loose fit soon becomes exaggerated. Composite pistons of aluminum and cast iron have been made in an effort to combine the advantages of lightness of material and.

greater heat conductivity found in aluminum with the small co-efiicient of expansion of cast iron. Leakage of oil and gasoline past the pistons has ,not been entirely eliminated however.

The object of my invention is to provide a piston which will belight in weight and adapted to preserve a'close fit with the cylinder walls at all times.

Another object is to construct a piston which will preserve a tight sliding fit with the cylinder walls and still avoid the usual rapid wear of the cylinder. i I

T hese, and other objects and advantages, which will more clearly appear in the description which follows, are accomplished by constructing the body of thepiston ot' a metal of light specific gravity, such as aluminum, and fitting outside said light Specification of Letters Eatent.

Patented Apr. 4., 1922.

Application filed. March 2?, 1921. Serial No. 454,398.

weight piston a thin sleeve of cast iron which will preserve a close fit with the cylinder and yet allow expansion of the piston without danger of seizing when the piston becomes heated. Also, by placing the sleeve in close contact with the cylinder walls and fitting the piston rings between the aluminum body and the sleeve I not only get a piston which will not leak, but one in which the piston rings do not scrape on the cylinder thus ivoiding wear of both the rings and the cylinder walls.

Referring to the drawing forming a part of this specification, and wherein like numerals of reference are applied to like parts throughout the several views. Fig. 1 is a central longitudinal section through a piston embodying my invention, and Fig. 2 is a side elevation thereof. My improved piston is made up of a piston head 1, which is preferably made of aluminum or some alloy of aluminum, so to obtain a light weight body for the piston. This head. is of the trunk type having a forward closed end. It has a rearwardly extending skirt 2 thereon which projects backwardly for a suiiicient distance to furnish a guide to prevent lateral slapping movement. On opposite inner sides of the hollow cylindrical head thus formed I provide the usual bearings 3 for the wrist pin 4. These bearings are formed by inwardly extending bosses The wrist pin 4 furnishes attachment for the connectingrod 0 in the usual manner. The rearward end of the skirt 2 1s prov ded with a diagonal kerf or slot 7 to accommodate a certain amount of lateral expansion of the material, due to heat.

The rearward en'd'oi theskirt 2 is threaded at 9 for the attachment of an outer cast iron sleeve 10. This sleeve I contemplate- .forming of an external,d1ameter very closely a certain amount of expansion of the piston relative to the cylinder, I may form a slot or kert' 11 diagonaily in the forward end of leakage of gas through the slot.

the sleeve similar to the kerf 7 in the skirt 2 previously described. This slot may be closed at some intermediate point by a transverse key or plug 8 Which will obviously not interfere with the free expansion of said sleeve butnvill serve to prevent appreciable To insure the sleeve 10 against unscrewin upon the threaded portion 9 I may providla a set screw 12 at some point along the threaded portion, the tightening of which within the sleeve and the skirt will prevent loosenin As will be seen from the drawing, the t betweenthe sleeve 10 and the piston head ,1 is a very loose one so as to provide for a certain amount of expansion of aluminum relative to the cast iron sleeve. To prevent leakage past the piston head and between the same, and the sleeve 10, I contemplate usingpiston rings 13, of some Well known and ef-- ficient type. to close the space between the two parts. Forming the-piston rings within the head so as to bear againstflthe sleeve 10 outside thereof will act also to force' the sleeve 10 resiliently against the walls of the cylinder so as to maintain a tight fit at all times. The provision of the slot 11 will however allow the sleeve .to exp-and a certain.

amount due to the heat, without binding against the cylinder walls. The piston rings will prevent leakage occurring between the sleeve and the head withoutthe usual wear which is caused by scraping of the piston rings upon the cylinder walls. There will in fact be very little wear. of the rings as there i will be no relatively longitudinal movement of the parts against which they hear. The scraping and scoring of thecylinder walls will therefore be largely avoided. It is believed that with this provision the life both of the pistonand the cylinder will be greatly prolonged.

This type of p ston will maintain a close 7 sliding fit-with the cylinder walls to an eX- tent not exceeded. by any oust iron piston now in use. By the use oi this piston I obtain the advantages of lightness and greater heat conductivity, due to aluminum, without the disz'ldventages usually encountered. And, by combining the cast iron sleeve 10 with the aluminum head, so that itcovers the entire periphery thereof, there will be no leakage pastthe aluminum head nor will there be ex- CSSl"B wear upon the aluminum piston itself 5 or upon the cylinder walls. The piston will maintain the desired close fit with the cylone that various changes in form and struc ,inder bothwhen cold or when heated, and the piston will operate eiliciently under the varied conditions of temperature and wear to which it is subjected.

Vhile I have illustrated one specific sin-p bodiment of my invention, it will be obviture may be made without-departing if ml the spirit of my invention and I do no, wish sleeve attached thereto, said fitting loosely over said head, said sleeve Z having a slit therein and piston ringsbe tween saidhead and said sleeve. i r

2. "A piston having ahead composed of aluminum, a rearwardly extending skirtQ- thereon having means to allow expansion thereof, a cast iron sleeve secured to the rear 1 end of said skirt and fitting loosely -over, and completely covering the cylindrical periphery of, said head. I I 3. A pi'ston having'a-head composedof a light gravity material, a rearwardly extend; ing skirt thereon, an outer sleeve ofiela tively heavier meta-l secured to said'iskin, 9 0 and spaced slightlyoutside said heildflmd piston rings between said head and sleeve.

A p e a i g a he qvof igm mny material, a skirtthereon of relativelylh 4 ier wear resisting material, m s t4; allow expansion of said head relative when sleeve, and means between said sleeve a'nd said head to prevent leakage therethrough.

5. A piston having a cylindrical headpf V- light gravity mater al, a skirt securedzto 5 spaced slightlytherefrom. except at the pointof attachment, and piston rings between said head and said sleeve, said sleeve being 11.0 slit adjacent said rings to allow said rings to press said sleeve resiliently outward.

7. In combination, a cylinder, a piston thereincomp'risinga loosely fitting alumi- -'.runn piston head, a cast iron sleeve .win- 11' pletely enclosing the periphery of said'head and secured theretoa'nd adapted to fit snugly against saidcylinder,.1neans to-ellow relative expansion of said head and said tween said head and said sleeve. y

8. A piston having a head, an outer sleeve being: slotted toward one end thereof and a transverse key or plug [closing said slot inter; mediate the ends thereof. 1 i In testimony whereof, I'hereunto aflix my Y iature, this'the 19th day of March, A. D.,

p n'oBER'r D." crow. I

sleeve and piston rings to seal the space l 

